DESCRIPTION: The purpose of the proposed research is to describe the dynamic aspects of the functional organization of the adult cortex. Sensory deprivation is one of the main causes of functional reorganization of the adult cortex, but due to technical limitations little is known about the spatiotemporal aspects of such reorganization as well as the structural changes that underlie it. The major emphasis of this proposal is the quantification of the functional and structural reorganization in the adult cortex following a reversible deprivation and recovery of the original function. The study will be applied to several levels of cortical cortical organization: cortical columns, intra- and inter column interactions, single-neurons, and intracortical anatomical connections by the application of several techniques to the same animal. To quantify the functional changes within the same animal before, during, and after deprivation-induced reorganization and recovery of the original function, the unique advantages of optical imaging of intrinsic signals will be exploited since it enables the repeated visualization of activity patterns and the functional organization of the living cortex with the highest spatial resolution currently available (50 um) in a chronic preparation. Moreover, the high-resolution map of functional organization obtained by imaging can serve as a guide for precise localization of electrodes to record and analyze activity from the neurons recorded simultaneously in areas that exhibit functional reorganization. In addition, the anatomical changes underlying this form of functional reorganization will be studied by injecting anatomical tracers to areas that show reorganization as visualized by imaging. The target of the proposed research is the "barrel cortex" subdivision of the somatosensory cortex of the rat. This area has unique advantages for the proposed study since it has a precise structural and functional representation of each whisker on the rat's snout and the whiskers are unique in their ability to regrow after deprivation thus allowing to study the results of reversible deprivation paradigm. The main objective of this proposal is to study the recovery of the original function following permanent versus reversible deprivation of tactile input form the whiskers. The study also includes the investigation of the effects of the following on recovery of the original function: different periods of peripheral deprivation, the effects of different types of deprivation (reduction versus elimination), and the use of different, complementary deprivation paradigms. This research has relevance to our understanding of the structural and functional processes that accompany recovery of the cortical function following damage to the periphery, especially those related to facial and dental organs, since the trigeminal system carries both whisker as well as other facial and dental sensory information in the cortex.